April
2, 2003 — Mark Twain once said the Mississippi River “cannot
be tamed, curbed or confined...you cannot bar its path with an obstruction
which it will not tear down, dance over and laugh at. The Mississippi
River will always have its own way, no engineering skill can persuade
it to do otherwise...” In 1993, the Mississippi River and the Missouri
River provided emphatic proof of Twain’s words. (NOAA image
of Iowa levee from the Great Flood of 1993.)

By the time
flood waters subsided in October, the Great Flood of 1993 had inundated
20 million acres in nine states, taking 50 lives and costing about $20
billion. Approximately 54,000 people were evacuated from flooded areas,
approximately 50,000 homes were destroyed or damaged and 75 towns had
been completely inundated. Some riverside communities were abandoned or
relocated to higher ground.

According
to the U.S. Army Corps of Engineers (as noted in the NOAA
National Weather Service natural disaster survey report) 40 of 229
federal levees and 1,043 of 1,347 non-federal levees were over-topped
or damaged. Every breeched levee contributed to the amount of flood water
flowing outside the main drainages. The flood eroded more than 600 billion
tons of top soil and deposited great amounts of sand and silt on valuable
farm land. In large areas inundated by the flood, the harvest of 1993
was a total loss and some farmers lost any chance for a 1994 harvest,
as well.

The entire
state of Iowa was declared a disaster area, as were portions of eight
other states: North Dakota, South Dakota, Minnesota,
Wisconsin, Illinois, Missouri, Nebraska and Kansas.

Flood
Timeline
Hydrologists at two NOAA National
Weather Service River Forecast Centers had warned that a wet fall
1992 and normal or above normal snowpack in the central United States
were setting the table for possible serious flooding when the spring thaw
hit in 1993.

Experienced
personnel at the North Central River Forecast Center in Minneapolis,
Minn., knew soils in the upper Mississippi River drainage basins were
too saturated to absorb much more rainfall. The same situation existed
for the Missouri River basin, which is monitored by the Missouri Basin
River Forecast Center, located at the time in Kansas
City prior to a move to a new office in Pleasant Hill, Mo. Heavy snowpack
in the Dakotas, Minnesota and Wisconsin, they warned, could be released
in a rush if certain weather patterns prevailed in the spring. Flood forecasters,
however, had no indication they were only months and weeks away from the
most costly and devastating flood to ravage the United States in modern
history.

“The
NOAA National Weather Service was just a few years into the modernization
that brought us new radars, satellites and other weather and hydrologic
tracking and forecasting tools, so, even though we knew there was strong
potential for continued flooding, we didn’t know the rains would
be so heavy and last for so long,” said Kenneth D. King, chief of
hydrologic services at the NOAA National Weather Service Central Region
Headquarters in Kansas City, Mo. “I think everyone was ready for
some short-term heavy rain and serious flooding, but nobody thought it
would last all summer.”

Late March
rains quickened the melting rate of snow on the ground and added volume
to the runoff in southern Minnesota and Wisconsin, feeding the headwaters
of the Mississippi River. At the same time the northern reaches of the
Missouri River were becoming saturated.

An annual
weather condition termed a Bermuda High (a high-pressure system that develops
in late spring off the southeastern U.S. coast and steers weather systems
across the eastern part of the country) had a few surprises of its own
in store for weather forecasters. The 1993 Bermuda High was of greater
intensity and moved farther to the north and west than usual. The High
formed an atmospheric dam over the Ohio River Valley and prevented storms
from following their normal course to the eastern seaboard. Instead, storms
kept re-generating over the central states, dropping record amounts of
rain on a nine-state area (North Dakota, South Dakota, Minnesota, Wisconsin,
Nebraska, Iowa, Illinois, Kansas and Missouri) primed for flooding.

“I
think the two most important aspects of the flood of 1993 were its intensity
and its duration,” King said. “That made it a historic flood.
This part of the country had never seen such heavy rainfall over such
a long period of time and had never experienced such heavy flooding over
such an extended period. The magnitude and duration of flooding were almost
overwhelming and it’s a tribute to the millions of people impacted
by the flood that they continued to battle to save their homes, farms
and communities. That perseverance is difficult enough to maintain when
flooding lasts for several days or a few weeks. To maintain it for the
duration of the flooding took incredible fortitude.”

Through the
course of the Great Flood of 1993, flooding occurred at approximately
500 Weather Service flood forecast points with record flooding recorded
at 93 forecast points (44 points in the upper Mississippi River drainage
and 49 on the Missouri). Some forecast points were above flood stage non-stop
for five months.

Producing
accurate flood and flash flood forecasts through all this was especially
difficult, King said, because the volume of water was so great it overwhelmed
the mainstem drainages. “In many locations, there was as much water
running outside the leveed river channels as there was running inside
the levees,” King said. “We had sufficient gauges to help
us determine the flow levels within the river basins but had to make educated
estimates about how much unaccounted for runoff was flowing outside the
levees.”

At St.
Louis, the first spring flooding on the Mississippi River was recorded
April 8, cresting at .2 feet above flood stage and lasting only that day.
The Mississippi rose above flood stage again on April 11 and stayed above
flood stage until May 24. The city got a respite as the Mississippi stayed
below flood stage May 24 to June 26. On June 27, the Mississippi again
went above flood stage and didn’t drop below flood stage for the
year until October 7—a total of 146 days above flood stage. The
Mississippi River was above the old record flood stage for more than three
weeks at St. Louis from mid July to mid August. Prior to 1993, the historic
flood of record on the Mississippi River at St. Louis had been 43.2 feet,
recorded April 28, 1973. That record was broken July 21, 1993, with a
level of 46.9 feet and broken again 11 days later with a record stage
of 49.58 feet on Aug. 1. St. Louis is located near the confluence of the
Missouri, Illinois and Mississippi rivers, all of which were in flood
at the same time.

During July,
central Iowa became the focus of media attention when flooding devastated
Ames and Des Moines. Record
rainfall July 8-9 pushed Saylorville Reservoir near Des Moines to a record
level for the third time in three weeks. The Racoon River flooded the
Des Moines water works, despite dikes that had been built six feet above
the flood of record, and flooded several electrical plants. More than
250,000 Des Moines residents were without electricity and without water.
At Ames, Squaw Creek flooding inundated Hilton Coliseum on the Iowa State
University campus with 14 feet of water.

Later in
July, Iowa City was impacted by the flood. The Iowa River at Iowa City
reached its second highest level ever, cresting at 28.21 feet July 19.
Water levels at Coralville Reservoir, about nine miles upstream from Iowa
City, peaked July 24 at 716.75 feet, the highest level recorded since
the reservoir was completed in 1958. Water went over the Coralville Reservoir
spillway from July 5 to Aug. 1, the only time in the reservoir’s
history the spillway had been topped.

Some locations
on the Mississippi River were in flood for almost 200 days while locations
on the Missouri neared 100 days of flooding. On the Mississippi, Grafton,
Ill., recorded flooding for 195 days, Clarksville, Mo, for 187 days, Winfield,
Mo., for 183 days, Hannibal, Mo., for 174 days, and Quincy, Ill., for
152 days. The Missouri River was above flood stage for 62 days in Jefferson
City, Mo., 77 days at Hermann, Mo.; and for 94 days at St. Charles in
the St. Louis metropolitan area.

At different
times, the survey report noted, flooding closed all bridges on the Mississippi
River from Davenport, Iowa, to St. Louis; and all bridges on the Missouri
River from Kansas City to St. Louis. Flooding forced closure of seven
of eight railroad lines in Missouri, as well as 12 commercial airports
and portions of interstate highways 29, 35 and 70 across the state and
of Interstate 64 to Kentucky.

In the prologue
for the disaster survey report, the NOAA administrator at the time wrote:
“Although the Great Flood of 1993 has caused devastating human,
environmental and economic impacts, the lessons learned will guide us
in providing improved services and benefits to the nation in the future.”

“Our
forecasters were highly complimented by emergency managers and others
for the accuracy of their weather and flood forecasts and vital information
provided through the flood of 1993,” King said. “That is a
great source of pride for us. Still, the Weather Service always strives
to improve its services and its efficiency.”

NOAA is dedicated
to enhancing economic security and national safety through the prediction
and research of weather and climate-related events and providing environmental
stewardship of the nation’s coastal and marine resources. NOAA is
part of the Department of Commerce.